Vapor detector



Oct. 6, 1953 c. s. PRESENZ 2,654,345

VAPOR DETECTOR Filed Nov. 7, 1952 v 4 Sheets-Sheet l v VISUAL METER AUDIOALARM 2L- BALLAST INVENTOR. F IG- 2 CECIL s PRESENZ A ATTORNEY Oct. 6, 1953 c. s. PRESENZ 2,654,845

VAPOR DETECTOR Filed Nov. 7, 1952 4 Sheets-Sheet 2 'C 28 OFF @rowen INVENTOR. CECIL S. PRESENZ FIG. 4 1

KM 4 0Mm ATTORNEY C. S. PRESENZ VAPOR DETECTOR Oct. 6, 1953 4 Sheets-$heet 5 Filed Nov. 7, 1952 FIG. 5

INVENTOR. CECIL S. PRESENZ FIG. 6

ATTORNEY C. S. PRESENZ VAPOR DETECTOR Oct. 6, 1953 ,4 Sheets-Sheet 4 Filed Nov. '7, 1952 Z E. w mm 5&8 520m T b m: mm mm mm mm fi a 6 Om m :1 w wwr mm: \mm Hmi m Q l wmgw www- ATTORNEY Patented Oct. 6, 1953 U "FFED STATE-S PATENT OFFICE decills hPresenz; Berkeley, Califgassignor to the United statesiof Ameri United ca asrepresented-by" the States Atomic Energy Commission aiiiiiianbiiniiie "136?1, 1952'; ser al No; siaz'ei The present invention relates to 'a' va'por detec tor. and more particulai'ly' to -alportab1e devicefot H detecting toxic concentrations of contaminants in' the atmosphere.

Vapor detectors of the quantitative--type'- have 6 been developed 'toioperateonnthe principle/than the. waporsatot be detected will. absorb light of certainrwave lengths. By determining thetquantity'oLlight absorbed, it i is possible .to indicate Whether the. concentration isatoxiceorrnoth The 10 present :diSCllSSiOIlaWill bev :limitedto .those vdetec-l tors Whichhave-been principallwdesigned .to ine dicate the presence of toxic concentrations ofs mercury vapor since rthe present inventiontliesfl the, past, there I is provided .lanultraviolet lamps htemits shth yine ai -wave. lenethtotzaafu Angstromsa o sincasuchuan ultraviolet larnpis ,i rc r ar-a ht Selma-L t w ll bej'lqle ln ,r

t 5 manimra a a the detector; can llbe le fit unatte ded. withont tea r that -amO IneIItaiy'Iine failure will render the i iv e lt 1- li t re e bit r t e, p em w tio rr 'to f provide a new and improved "vapor do- 3 tector A O hr sh eh i 't tio tli tiz the chajnaber;

jecte df'subs tantially without reflections iro vide a vapor detectorin which the components! have been designed to operate in a small portable carryingtcase.

Anotheruimportant .objectiof the invention is to same 'source 'of ultraviolet-light.

fi Cl aiins. (01. 256 -435) v e a e y; on tr cted an r q-t nutiiz-n ing' simple circuitry and which is sensitive but simple to operate. s y I Other objects and advantages of the invention Will jbe apparent from the following description. and claims considered together with the accompanying drawing; in which: l A F'gure 1 is a schematic diagram of the invention; i, a F

Figure 2 is a wiring diagrammi-an-ultraviolet; lamp starting circuit for; theinventiongotFig 1;; Figure-3 is a plan view of--the presentinvention of Figil as mounted-in a portable carrying-case-;---; Figure 4 is an elevational view of the invention as shown in Fig.3;-- in Figure 5 is a sectional View ofthe'vap'or chamber of the invention taken along the line 5-5 of mgr-4; l p m: l i a Figure 6 is a V1 w taken along the line 6-6 of Figure 7 is a view taken along the line 'l'! of Fig. 6; and Y .3 Figureeflis a wiring diagram of the circuit of iithewinventionr L Referring to thedrawing, Fig. 11inparticular itfl is to be lnotedlthat there is provideda t-balanced. networkcomprising two parallel-connected com-p binations H and 12.0faseries-connected photof-s. tube I3, 14 and resistor l6, l1, respectivelymfl hen junction between the twophototubestl3gwi4 is con? nected to i a source l8 of; positive potential :avhiieu the: junction betweenqthe two resistors I5, I! is connectedi to ground ltwo-phototubes Mandy is acylindrical-tube lfi -i-ormir g a vapor chambers -,-a ra o e -lam Hand a ariam-151101.1- order To determine unbalance COI1difiiOIlS "between the-.two combinations 1;} and ,l 2; a1 bl'ide; circuitl z i is-connected between points ZEQand 2 1 o rep t v ly,- .1 .l-eutpuw ri e circuit 24 is connectedqtoa seleotoltrswitch- 2 8, 11 p t o 1. o ich r sk s n ted to? n aud om alarm-nnit 33, two positions-32 and-23mm a visualmeter 35, anduai finahposition 31 to a remote connection terminal- 38am J my From such general description of the invention it will; be apparent that the bridge circuit 24 can, be balanced when-the chamber 2 lisclear of. vapor by ,adjustingthe irisy23 us r-that equal. quantities of light, rom the ultraviolet lamp ,22 reach the p phototubes I3 and l d ls uch iris-23 1541806552113; beeausathe two phototubes are placed different: distances from the 1arnp,g 2. ,M(ith the bridge uit. 24 e an dini u h m nn r hzi c ua lated through the chamber 21. When a vapor Disposed betweenthe Still another object of the invention is to pro- 55 enters the chamber 2| which absorbs light of the wave length of the ultraviolet light (2537 Angstroms), the quantity of such light reaching the phototube 3 is decreased to unbalance the bridge. The unbalance then results in an output voltage from the bridge circuit 24 and is transmitted to the selected one of the audio alarm unit 33, the visual meter 35, or the remote terminal 38.

Referring now to Figs. 3 and 4 of the drawing, it is seen that there is provided a portable carrying case 4| for the invention and having, in addition to enclosing walls 42, a front panel 43 for mounting necessary controls, and a chassis 44 for rigidly mounting the circuit elements. Mounted conventionally on the panel 43, internally of the case 4|, is the assembly comprising the cylindrical tube l9, phototubes l3 and I4, ultraviolet lamp 22, and iris 23. Such assembly is preferably made unitary and in a lighttight manner. The vapor chamber 2| itself is formed by the elongated metallic cylinder I9 which is open at either end (see Fig. 5) and pro vided with flanged portions 46 at such ends. An intake pipe 4'! is mounted transversely of the cylinder I9 in communication therewith and an outlet pipe 48 is similarly mounted at the other end. Mounted within the cylinder I9 between the inlet and outlet pipes 4'! and 48 are a plurality of bafiles 5| having aligned apertures 52 therein. Preferably such ba-flies 5| are of a nonreflective material, such as rubber, and of a dimension which prevents light reflections from the interior wall of the cylindrical tube :9 reaching the end of the chamber 2|. To provide for movement of air and vapor through the chamber 2|, a motor driven exhaust fan 56 is mounted on the outlet pipe 48 with an exhaust pipe 5! extending therefrom.

A housing BI is suitably mounted as by screws 62, on the flange 46 at the intake end of the cylinder I9 with a light and gas-tight seal 63 clamped therebetween. Also, sealed between the housing BI and the flange 46 is a window 6 preferably quartz, which is transparent to light having a wave length of 2537 Angstroms. Disposed axially within such housing BI is the phototube l3 with the window thereof aligned with the window 64. The electrical connections of the phototube I3 have been stated previously in general terms and will be discussed in detail hereinafter.

At the other end of the chamber 2| a second housing 66 is similarly mounted by screws 6'! to the flange 46 of the metallic cylinder [9; i. e., a seal 68 and quartz window E9 is clamped between the second housing and the cylinder. Suitably mounted within the housing I56 is the ultraviolet lamp 22 so that the light therefrom is projected through the chamber 2! toward the phototube. In the illustration of the invention (Figs. 3-5), it is to be noted that a second light channel, comprising a tubular extension H extends from the housing 66 at right angles to the center line of the chamber 2! and is terminated in a third housing 12. Such arrangement has been provided to decrease the longitudinal dimension of the combination for mounting within as small a longitudinal dimension as possible. Disposed within the housing i2 is the other phototube l4 so that light extending through the passage H from the ultraviolet lamp 22 will fall upon the light-sensitive element of the phototube. The electrical connections for the ultraviolet lamp 22 and phototube I 4 will be set forth in detail hereinafter.

So that the bridge circuit of which the phototubes I3 and I4 are parts can be balanced, an

iris 23 is mounted within the extension 'H between the ultraviolet lamp 22 and the phototube I4. A cylinder I3 having one end closed except for a circular aperture 14 therein is disposed in a fixed position within the extension H. Disposed adjacent the closed end of the cylinder I3 is a rotatable disk I6 having an aperture H in the shape of a comma with the circular portion thereof aligned with the aperture 14 in the cylinder 13 and the tail portion extended so that the center of the disk lies along a line extended from the center of the circular portion to the tip of the tail portion. Thus, when the disk I6 is rotated from the position, whereby the two apertures I4 and TI are aligned to allow a maximum quantity of light to traverse the apertures, the opening is gradually decreased until the passageway is entirely blocked. To permit manual rotation of the disk I6 from outside the extension 'II, a slot 18 is provided to extend substantially degrees about the periphery so that a screw '29 projecting through a slide block BI threadedly engages the disk 16. A second cylinder 82 is disposed within the extension H with one end abutting the opposite face of the disk 16 to maintain the disk in position.

Now consider the electrical circuitry of the invention in detail (see Fig. 8). There is pro vided a conventional power supply 9| having the input terminals 92 and 93, respectively, connected to a source of alternating current 94 through a switch 96 and fuse 91. One positive terminal 98 of such power supply 9| is directly connected to the junction between the phototubes I3 and I4 to furnish a suitable operating potential. A resistor IBI, a parallel-connected resistor [02 and potentiometer I83, and a resistor I04 are seriesconnected from the phototube I3 to ground. Such resistances were lumped into a single resistor I6 in Fig. 1 for convenience. Also, a singlepole, single-throw switch I06, a resistor I01, and

a resistor I08 are series-connected between the phototube l4 and ground. Here again the resistors I01 and I08 were combined as esistor I! in Fig. 1 for the general description.

The variable arm of the potentiometer N33 is connected through a limiting resistor III to the control grid of a triode vacuum tube H2, the cathode of which is connected through a resistor H3 to ground and the anode of which is connected to one side of a potentiometer H4. A second triode vacuum tube H6, similar to tube 2, is connected with the cathode grounded through a resistor H1, the control grid connected through a limiting resistor H8 to the junction between the resistors I91 and H18 in the branch I2, and the anode directly joined to the other side of the potentiometer H4. Now with the variable arm of the potentiometer H4 connected to a second positive terminal H9 of the power supply 9|, it is readily seen that the connections of the tubes H2 and I I5 are that of a conventional vacuum tube voltmeter circuit with the potentiometer H4 available to balance the conduction of the tubes and the potentiometer I93 providing for establishing the zero set of the circuit.

The cathode of the tube I I5 is connected to the swinging arm of the previously described selector switch 23. The terminal 32 of the switch 28 is connected to the adjustable arm of a potentiometer I2I, the terminal 34 to the adjustable arm of another potentiometer I22, the ter-- minal 3| to the adjustable arm of still another ments I62 and I63 of the lamp. Upon discharge of the capacitor I'II through the solenoid I66 of the relay I6! the relay is actuated to open the contacts I14 and H9 which results, because of the ballast I13, in voltage transients such as to cause an are between the filaments I62 and I63 within the lamp 22. Once the arc has been initiated through the lamp 22 the normal voltage across the lamp is sufiicient to maintain operation thereof. The current path for the lamp 22 then may be traced from the positive terminal III! of the power supply 9|, through the potentiometer II'I, through the ballast winding I76, through the tube 22, through the solenoid I66, through the resistor I63, and through the indicating lamp I69 to ground. From the foregoing it will be readily apparent that should the operation of the power supply 9I be interrupted momentarily the relay I6? will assume its normal starting position and the starting sequence will b commended to re-energize the lamp 22.

With the lamp 22 in operation the two tubes I I2 and I I6 of the bridge circuit may be balanced by adjustment of the potentiometer H4. Next with the switch I66 closed, fresh air in the chamber 2|, and the switch 28 in position 32 for large range reading the potentiometer I63 is adjusted for a zero setting on the visual meter 36. To calibrate the instrument the switch I36 is opened and the potentiometer I2! adjusted for full scale deflection. To set the other scale, X10, of the visual meter 36 the potentiometer I63 is set for a reading of one-tenth scale when the switch 28 is in position 32 so that by changing the switch 28 to position 33 the potentiometer I22 may be adjusted for a full scale deflection. Finally the switch 28 should be returned to position 32 and the potentiometer I63 readjusted for zero setting when the switch I66 is closed;

A mercury calibration may be made after the foregoing preliminary adjustments have been completed. For such calibration a small bottle of mercury (at a temperature of substantially twenty degrees centigrade) is required. The surface of the mercury should then be placed adjacent to, but not touching, the intake to the cylinder I9. Under such circumstance a reading of substantially I8 percent of the large range, IQ, of the visual meter 36 should be obtained which has been determined to be equivalent to a concentration of 3.2 milligrams of mercury per cubic meter. Should the foregoing reading not be obtained, it is advisable to recheck the preliminary adjustments and to determine that there has been no contamination of the intake and chamber system.

To test for mercury contamination of the intake and chamber system; there is provided the switch I51 which opens the circuit of the exhaust fan motor 56. With the bridge circuit properly adjusted prior to opening the switch I61, there will be a definite positive deflection after the blower has been stopped provided contamination has occurred.

There remains but one further adjustment necessary prior to actual monitoring operations and this is to set the sensitivity of the audio alarm unit. With the switch 28 in position 3I the potentiometer I23 is adjusted so that the relay I24 operates at a desired vapor level. Such adjustment may be readily made without the use of mercury vapor by using the zero set potentiometer I63 so that the equivalent of 0.1 milligram of mercury per cubic meter may be registered on the visual meter 36. Operation of the relay I24 closes the contactor I26 thereof so that a positive voltage appears at the control grid of the gaseous discharge tube I3I in phase with a positive voltage impressed at the anode of the tube through the solenoid I32 of the relay I33 during each positive half cycle of the alternating voltage of the source 94. The result of such operation is that the tube I3I is alternately conductive and non-conductive in accordance with the frequency of the alternating voltage and current flows through the solenoid I32 of the relay I33 only when the tube is conductive. Each time current flows through the solenoid I32 of the relay I33 the relay is operated to close the contactor I36 and open the other contactor I34. The opening of the latter contactor serves to decrease the voltage across the tube I3I as a protective measure once conduction has been started. The closing of the contactor I36 completes the circuit from the positive output terminal I5I of the power supply 9| to the anode of the oscillator tube I46. The circuit connections of such oscillator tube I46 are conventional so that an audio frequency voltage is transferred from the anode circuit to the load speaker I54 in pulses according to the operation of the relay I33.

In use the vapor detector is placed in the locale to be monitored after the foregoing adjustments and calibration have been satisfactorily accomplished. Usually it is desirable to operate without a constant observer and so the switch is set to position 3|, audio alarm. Now ith suitable power connected to the power supply 9i and the circuit otherwise in condition for operation, any mercury vapor present in the atmosphere will be drawn into the chamber 2| through the intake by the action of the fan 56. The mercury vapor present in the chamber 2| absorbs a portion of the ultraviolet light projected therethrough from the lamp 22. Such absorption results in an unbalance of light reaching the respective phototubes I3 and I4 and thereby causes a differential in voltage at the cathodes of the tubes H2 and H6 in the bridge circuit. When an unbalance voltage condition exists to such an extent that the relay I24 is energized a pulsed audio frequency sound is produced at the speaker I54 to warn that the toxic limit of mercury vapor in the atmosphere has been reached.

From the foregoing it will be readily apparent that a vapor detector has been provided which may be used for local warning either by indicating to an observer the presence of a toxic amount of vapor, or by generation of an audible warning signal, or further by remote warning as provided by the terminals 38 and I28 suitably connected to a remotely positioned indicator. It is also to be noted that the present vapor detector is extremely stable regardless of variations in line voltage because of the automatic start circuit for the ultraviolet lamp and the use of two phototubes viewing the same source of ultraviolet light.

While the salient features of the present invention have been described in detail with respect to one embodiment it will, of course, be apparent that numerous modifications may be made within the spirit and scope of the invention and it is therefore not desired to limit the invention to the exact details shown except insofar as they may be described in the following claims.

What is claimed is:

1. In a portable mercury vapor detector, the combination comprising a mercury vapor lamp,

automatic starting means connected to said lamp, an elongated cylinder forming a sample chamber disposed with one end adjacent said lamp, a plurality of apertured baffles mounted in spacedapart relation within said cylinder with the apertures in alignment, intake and outlet means mounted transversely of said cylinder at opposite ends thereof, a window transparent to ultraviolet light sealed across either end of said cylinder, blower means mounted on said outlet means to provide a continuous flow of air to b monitored through said cylinder, a tube disposed with one end adjacent said lamp, a second phototube disposed at the other end of said tube, a balanced parallel circuit including said first phototube in one branch and said second phototube in the other branch, a bridge circuit connected between equal voltage points of the branches of said balanced parallel circuit, and indicating means connected to said bridge circuit.

2. In a portable mercury vapor detector, the combination comprising a mercury vapor lamp, automatic starting means connected to said lamp, an elongated cylinder forming a sample chamber disposed with one end adjacent said lamp, a plurality of apertured bafiies mounted in spacedapart relation within said cylinder with the apertures in alignment, intake and outlet means mounted transversely of said cylinder at opposite ends thereof and communicating with said chamber, a window transparent to ultraviolet light sealed across either end of said cylinder, blower means mounted on said outlet means to provide a continuous flow of air to be monitored through said cylinder, a tube substantially shorter than said cylinder disposed with one end adjacent said lamp, means disposed within said tube to restrict the light passage therethrough, a second phototube disposed at the other end of said tube, a balanced parallel circuit including said first phototube in one branch and said second phototube in the other branch, a bridge circuit connected between equal voltage points of the branches of said balanced parallel circuit, and indicating means connected to said bridge cirunit.

3. In a portable mercury vapor detector, the combination comprising a mercury vapor lamp, automatic starting means connected to said lamp, an elongated cylinder forming a sample chamber disposed with one end adjacent said lamp, a plurality of apertured baflles mounted transversely in spaced-apart relation Within said cylinder with the apertures aligned along the axis thereof, intake and outlet pipes mounted transversely of said cylinder at opposite ends thereof and communicating with said chamber, blower means mounted on said outlet pipe to provide a continuous flow of air to be monitored through said chamber, a tube substantially shorter than said cylinder disposed transversely of said cylinder with one end adjacent said lamp, an adjustable iris disposed within said tube to restrict the light passage therethrough, a second phototube disposed at the other end of said tube, a balanced parallel circuit including said first phototube in one branch and said second phototube in the other branch, a bridge circuit connected between equal voltage points of th branches of said balanced parallel branches, a visual indicator, an audio alarm, and a selector switch connected to said bridge circuit and selectively to said indicator and audio alarm.

4. The combination of claim 3 wherein the automatic starting means for the mercury vapor lamp comprises a source of potential, circuit means for connecting the filament of said lamp in series with ballast windings across said source of potential, said circuit means including a relay for interrupting the external series: connection between the filaments of said lamp when an internal discharge between such filaments is established.

5. The combination of claim 3 wherein the automatic starting means for the mercury vapor lamp comprises a source of potential, a ballast unit having a first and a second winding, one end of said first winding being connected to one side of said source of potential and the other end being connected to one filament of said lamp, a relay having a solenoid and at least one normally closed contactor, said one filament being further connected to one side of said second winding through said contactor, the other side of said second winding being connected to the other filament of said lamp, such other filament being connected to the other side of said source of potential through said solenoid.

6. The combination of claim 3 wherein the automatic starting means for the mercury vapor lamp comprises a source of potential, a free running electronic oscillator connected across said source of potential, one filament of said lamp being connected to one side of the output of said oscillator and the other filament of said lamp being connected to the other side of said oscillator, and a ballast winding connected between the other connections of the two filaments of said lamp.

CECIL S. PRESENZ.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,369,966 Hawkins Feb. 20, 1945 2,407,838 Kliever Sept. 17, 1946 2,617,940 Giguere Nov. 11, 1952 2,621,297 Obermaier Dec. 9, 1952 2,632,114 Silvertooth Mar. 17, 1953 

